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Changes of the second suppressive period (ES2) of the exteroceptive suppression of the temporalis muscle activity are found in patients with chronic tension-type headache (TTH) and are suggested to reflect an abnormal endogenous pain control system. We investigated whether similar changes are found in patients with the fibromyalgia syndrome (FMS) that is also believed to result from disturbed central pain processing. The ES2 values of 27 patients with FMS were compared with those of 18 patients with TTH and 40 healthy volunteers. The duration of ES2 (+/-SD) in FMS patients was 30.6+/-7.5 ms and was not significantly different from the control group (33.1+/-7.8 ms), whereas it was significantly shortened in TTH patients (22.9+/-11.5 ms). Our results indicate that, despite similar concepts on the pathophysiology of the two chronic pain disorders, there are no comparable changes of this brain stem reflex activity in FMS.

During single word processing the negative cortical DC-potential reveals a left frontal preponderance in normal right-handers as well as in patients with a history of transient aphasia. Lateralization of DC-negativity therefore provides a reliable and robust method for the assessment of language dominance. In 11 stroke patients with permanent aphasia this physiological pattern changed to bilateral activation reflecting an additional right-hemispheric involvement in compensatory mechanisms in aphasia. Along with complete clinical recovery the classical aphasic syndromes revealed specific differences in changes of their lateralization patterns. In Broca's aphasia the initial right-hemispheric preponderance changed to a left frontal lateralization while in Wernicke's aphasia a presumably permanent shift towards the right hemisphere occurred. Differences in lateralization patterns might reflect different mechanisms of recovery such as the initial disinhibition of homologous areas contralaterally and subsequent collateral sprouting and synaptic modulation. The assessment of changes in lateralization of the cortical DC-potential during language tasks in a non-invasive, safe method with excellent time resolution that might provide further insights in the neural basis of recovery from aphasia.

We compared the diagnostic sensitivity of traditional visual tests such as the Snellen-test and pattern reversal VEPs with psychophysical and electrophysiological tests involving motion processing and psychophysical tests of contrast processing in detecting visual deficits in a group of MS patients. A total of 30 patients with a definite diagnosis of MS and 22 age-matched controls selected from a pool of healthy volunteers participated in this study. Visual evoked potentials elicited by reversing checkerboards and moving random dot patterns (motion-onset VEPs) were recorded. The recognition of motion-defined forms (motion-defined letter test, MDL-test) and of contrast reduced optotypes was measured psychophysically. Of 30 patients, 29 showed deficits in at least one of the tests applied. The highest detection rate was obtained for a simple psychophysical test, the MDL-test, which revealed abnormalities in 80% of the patients. This is about 12% more than pattern VEPs could detect. Conversely, abnormalities in motion-onset VEPs were found in only 16% of the patients. Our results show that by adding a simple psychophysical test of form-from-motion analysis our capability to demonstrate an involvement of the visual system in MS patients may be promoted considerably.

We have developed a method to observe and quantify the phasic relationship between the burst patterns of antagonistic muscles in any roughly periodic movement, such as tremor, for up to 24 h. This paper describes our approach, in which long-term EMG recordings are evaluated by a procedure based on cross-spectral analysis. The method is then illustrated by data from 6 patients with essential tremor. Our data confirm earlier observations that a particular patient may show different burst patterns at different times. However, as opposed to tremor analysis based on short-term recording, our method allows quantitative statements on the relative frequency of the burst patterns, as they occur under everyday conditions. In addition, our data suggest that in ET (a) alternating tremor activity in one hand may occur simultaneously with synchronous activity in the other hand; (b) along with the classical alternating and co-contracting patterns there may be significant 'non-classical' activity, that cannot be called alternating or synchronous.

Patients with idiopathic Parkinson's syndrome, most of them in early stages of the disease, and matched healthy controls participated in a continuous performance task while their EEGs were recorded from 15 electrodes. During preparation of movements, a contingent negative variation (CNV) maximal at central and posterior sites was visible. This CNV was reduced in the patient population. A large P3-like positive deflection occurred after go and no-go stimuli that called for execution (go) or suppression (no-go) of a button press. Compared to healthy controls, the positive wave in Parkinson patients was significantly reduced after go stimuli and maximally attenuated when no-go stimuli had indicated to suppress the motor response. In contrast, P3 amplitudes after irrelevant "ignore' stimuli was not significantly reduced in the patients. These results are interpreted in the framework of a model of striatal function postulating (i) that populations of cortical and striatal neurons form distributed functional units (Hebbian cell assemblies), and (ii) that mutual inhibition between such cortico-striatal cell assemblies is mediated by the neostriatum, the forebrain structure primarily affected in Parkinson's disease.

Cerebello-cerebral interaction plays a fundamental role in movement processing. Extensively studied in monkeys, cerebello-thalamo-cerebral information processing is less clear in humans. Taking advantage of the tight linkage between cerebellum and cerebral motor cortex, the objective of this experiment was to gain information on cerebellar function, dysfunction and recovery by analyzing movement-related cortical potentials (MRCPs). MRCPs were recorded prior to voluntary repetitive finger movements from two cerebellar stroke patients, in the acute phase of cerebellar stroke and after clinical recovery. Ten normal subjects served as controls. The main result was a significant depression of late MRCP components over the contralateral motor cortex when patients performed index finger movements of the affected side in the acute phase, and improvement of depressed components after clinical recovery, 8-10 months later. Topographic maps of late MRCP components showed diffusely enlarged potential fields with ataxic movements in the acute phase, and re-focused fields on follow-up. We conclude that (1) late MRCP components are particularly sensitive to cerebellar input in humans and can reflect different functional states of the cerebellum, (2) disturbance of motor cortex function after cerebellar stroke (diaschisis) can occur as a temporary phenomenon that reverses with good clinical recovery.

We have developed a method of long-term EMG recording that has proven suitable for the quantification of pathological tremor. In the present paper we show that the principal parameters of the method (tremor occurrence, tremor intensity, tremor frequency) are highly reproducible and that the method is specific and sensitive for detection of pathological tremor. Twelve patients with essential tremor (ET) and 13 patients with Parkinson's disease (PD) were recorded repeatedly on 3 successive days. For each patient group and for each parameter the intersubject variability was much larger than the intersubject variability. The intraclass correlation coefficient "R" was in the order of 0.9 for each parameter and the mean of Pearson's correlation coefficient between successive days was also approximately 0.9. Recordings from normal controls demonstrated that the method's specificity for pathological tremor is 94.1% and its sensitivity is 96%.

Compound muscle action potentials (CMAPs) were recorded from anterior tibial (TA) and soleus (SOL) muscles following transcranial magnetic stimulation of motor cortex in 10 healthy subjects: (1) while standing upright without support, (2) while sitting, and (3) while lying supine. The results of this study demonstrate a significant influence of posture upon the amplitudes of CMAPs. Postural facilitation presented itself, firstly, in terms of a higher incidence of bilateral activation of distal leg muscles during stance and, secondly, as significant enhancement of the amplitude of CMAPs while standing as compared to lying supine. The onset latency, however, did not disclose a significant shortening during stance. To assess the effects of preinnervation subjects voluntarily adjusted the level of TA activity to 5%, 10% and 20% of maximum isometric force respectively before cortex stimulation. Voluntary background contraction resulted in a significant increase of amplitude of CMAPs but, in contrast to postural facilitation, concomitant with a significant decrease in onset latency. These results point to a somewhat different mechanism of facilitation during stance as compared to voluntary preinnervation. But it cannot be decided whether cortical mechanisms, different descending systems, the spinal circuitry or a combination of these factors is responsible for the observed effects.

Posturography was performed in 41 patients with cerebellar diseases by means of a force measuring platform using an on-line computer program which calculated sway path, sway area, antero-posterior and lateral sway components and the amount of visual stabilization. Postural ataxia was quantitatively studied in 8 patients with spinal ataxia (Friedreich's), 6 patients with vestibulocerebellar lesions, 11 patients with anterior lobe atrophy, 7 patients with hemispheral cerebellar lesions, and 9 patients with a disease affecting all parts of the cerebellum. Patients with lesions of the cerebellar hemispheres could not be separated from normals by means of posturography. Lesions of the spino-cerebellar afferents (Friedreich' ataxia) caused an omnidirectional low frequency sway with preserved visual stabilization. Patients with anterior lobe atrophy showed a predominant antero-posterior sway, often with a spontaneous high frequency body tremor around 3 Hz. Vestibulo-cerebellar lesions exhibited omnidirectional low frequency sway poorly stabilized by vision. Quantitative posturography helps to localize cerebellar lesions and allows for quantitative follow-up studies of cerebellar diseases.

The present study compares the results of sensory evoked potentials after stimulation of the tibial nerve with measurements of short (M1), medium (M2) and long-loop latency (M3) responses of leg muscles in 42 patients suffering from multiple sclerosis. EMG responses were elicited by a movable platform which was tilted in pitch toe-up around the subject's ankle joint. The short latency response of the triceps surae muscle was nearly always normal in latency. The M2 response was lacking in about 30% of the patients and 10% of normals. The long latency response (M3) in the antagonistic anterior tibial muscle was significantly delayed (beyond 162 msec = AM + 2.5 S) in 69% of the patients. The delayed M3 response was found to indicate demyelination as reliably as the delayed somatosensory evoked potential (66% of the patients). The frequency of coincident results in the entire group was 86%. Additional information is gained in cases where SEPs are normal, but M3 is delayed (7%). Furthermore, patients lacking P40 of the SEP still exhibit M3 responses, the latency of which may be measured (24%). The results favour the assumption that M3 is mediated by a supraspinal pathway.

In order to elucidate further the possible pathways and the functional significance of long-loop reflexes we recorded short-, medium- and long-latency responses from leg muscles in 27 patients with spinal lesions, 20 patients with central lesions of the internal capsule or cerebral hemisphere, and in 18 control patients with frontal or occipital lesions without motor or sensory disturbances. Our normal population included 50 subjects, who were age and sex matched to the patients. The mean latency of the long-latency response (LL) in the anterior tibial muscle was significantly delayed in patients with spinal (164.5 msec) and central lesions (145.1 msec) compared to control patients (123.5 msec) and the normals (125.3 msec). This delay of LL could be observed in patients who exhibited only motor or sensory disturbances or a combination of both. The medium-latency response (ML) was absent in 47% of the records in patients with spinal lesions, mainly on the side which was clinically more affected. Its latency was normal if the response occurred. The integral of the LL response was enlarged in patients with spinal or central lesions, but was also enlarged in the control group. The results indicate that the ML response is segmental, but that its amplitude is modulated by supraspinal structures. The LL response probably corresponds to a transcortical 'reflex.'